The present invention relates to a slot antenna assembly, and in particular to a slot antenna having an apparatus for conveniently adjusting the operating frequency band of the slot antenna.
There is a growing need for slot antennas for use in wireless communication devices. A conventional slot antenna assembly, disclosed in U.S. Pat. No. 6,150,989, comprises a body made from a metal foil with an elongated, narrow slot defined therein, a cable having an inner core wire soldered to a flat surface at a first feed point near the slot and an outer shield soldered to the flat surface at a second feed point near the slot and opposite the first feed point, and diodes secured across the slot at a predetermined location. When the antenna is used in a transmission mode, at least one of the diodes can conduct, short-circuiting a portion of the slot and effectively reducing the length of the slot to a distance between the location of the diodes and the first and second feed points. The operating frequency band of the slot antenna can be changed by changing the location of the diodes.
However, changing the operating frequency band requires that the diodes be removed from the antenna and then soldered to another location crossing the slot. The procedure is inconvenient. Furthermore, such a change adjusts the operating frequency band of the slot antenna discretely, not continuously, so it is difficult to set an optimal operating frequency band of the slot antenna.
Hence, an improved antenna assembly is desired to overcome the above-mentioned shortcomings of existing antenna assemblies.
A primary object, therefore, of the present invention is to provide an improved slot antenna assembly having an adjustable tuning apparatus for changing the operating frequency band of the antenna conveniently over a continuous range.
An antenna assembly in accordance with the present invention comprises a slot antenna body comprising a metal foil defining an elongated slot therein, an adjustable tuning apparatus movably mounted to the slot antenna body and a coaxial feeder cable. The adjustable tuning apparatus comprises a conductive holding portion, a conductive slide portion and an insulative connecting portion connecting the holding portion with the slide portion. The coaxial cable comprises an inner core wire which is electrically connected to the slot antenna body through the holding portion and an outer shield which is electrically connected to the slot antenna body by the slide portion.
The adjustable tuning apparatus can slide along the slot to change the operating frequency band of the antenna body.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description of a preferred embodiment when taken in conjunction with the accompanying drawings.